1. Field of the Disclosure
The present disclosure generally relates to the field of sensing or detection of presence of high voltages on electrical conductors in AC (alternating current) power distribution systems, and, more particularly, to a high voltage sensing capacitor with electrodes having an incomplete or partial overlap and are substantially completely encapsulated within an insulator body.
2. Brief Description of Related Art
High voltage single and multi-phase AC (alternating current) power sources are utilized in many industries. The use of high voltage AC power distribution systems is accompanied by the risk that electrical maintenance personnel (and others) may inadvertently come into contact with energized conductors and be electrocuted or seriously injured. Thus, it is desirable to safely determine if a particular segment of an electrical bus is energized. Such determination of existence or magnitude of these high voltage conditions may prevent human injuries or deaths.
U.S Pat. No. 5,065,142 (“the '142 patent”) discusses a safety apparatus for indicating a live AC voltage condition in an insulated electrical conductor having a central conductor wire. A capacitor is constructed around the insulated conductor so the high voltage central conductor wire within the insulation forms an inner electrode of the capacitor and the conductor insulation forms the principal dielectric of the capacitor. The outer capacitor electrode is slidably placed onto the insulated conductor. Such capacitor provides a high impedance circuit through a gas discharge lamp to ground. The current through the capacitor is sufficient to cause the discharge tube to glow when the high voltage circuit is energized, thus providing a visible warning to maintenance personnel. Each of the three phases of an electrical distribution network can be independently monitored in this manner.
The safety apparatus discussed in the '142 patent may not be suitable to be attached to a busbar in a piece of switchgear. Hence, a busbar-based voltage sensing device may be desirable for higher voltage applications.
Furthermore, it is observed here that some existing high-voltage interface apparatus are constructed such that the electrodes and the dielectric material of the capacitive interface are exposed to air. This exposure to air may create corona and fringing, which may in turn create a partial discharge condition. The partial discharge may cause a continual degradation in the capacitor's dielectric material that may eventually cause a “punch-through” dielectric failure. Such a failure may be catastrophic and irreversible. The dielectric failure may not only render the capacitive interface useless to provide the voltage sensing functionality, but may also create potentially unsafe and hazardous short-circuit conditions on high-voltage conductors. Hence, it also may be desirable to provide a high-voltage sensing device that can avoid potentially destructive partial discharges when used under ambient surroundings.